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Biomedical subjects

H Zhang

Publications and source records attributed to H Zhang.

At least 487 records · Page 27Linked to original sources
PubMed2001

[Soft tissue profile changes after maxillary protraction in complete unilateral cleft lip and palate patients].

OBJECTIVE: The purpose is to evaluate the soft tissue profile changes in patients with complete unilateral cleft lip and palate treated after maxillary protraction. METHODS: 12 patients with complete unilateral cleft lip and palate were treated using maxillary protraction. Lateral cephalometric films were taken before and after treatment. Soft tissue profile changes were evaluated by comparing the difference of soft tissue landmarks between two films. RESULTS: After maxillary protraction, the convex of nose (S-Ns-PRN) increased significantly (P<0.001), the convex of maxillary soft tissue was increased by 3.8 degree (P<0.01). The convex of middle face changed significantly (P<0.01). In mandible angle S-Ns-SM was decreased one degree (P>0.05). Vertically, there was no significant difference in upper face height (P>0.05). Total face height increased significantly (P<0.01). CONCLUSION: After treatment of maxillary protraction, the soft tissue profile in patients with complete cleft lip and palate improved significantly.

English Abstract↗
PubMed2001

[Posterior stabilized knee arthroplasty: 5-year follow up].

OBJECTIVE: To evaluate the middle-term results of posterior stabilized knee arthroplasty (PSKA). METHODS: From July 1995 to July 2000, 19 knees of 18 patients were replaced with posterior stabilized prosthesis (Insall-Burstein II). Among the patients, 2 were male, and 16 female. Their average age was 62.5 years (44-78 years). One patient was operated on bilaterally. Preoperative diagnosis revealed osteoarthritis in 16 knees, and rheumatoid arthritis in 3 knees. Four knees demonstrated severe bone deficiency during surgery. Before operation, 15 of the rest knees were varusly deformed, 4 were valgusly deformed, and 8 had flexion contracture. Two patients underwent surgery previously. 17 patients (18 knees) were followed-up for 41-60 months, each of them was evaluated with the Special Surgery Knee Scoring System. RESULTS: Average preoperative scores increased from 62 preoperatively to 89 postoperatively. The range of motion was significantly improved from 91 degrees preoperatively to 115 degrees postoperatively. Eleven knees were rated as excellent, 5 good, 1 fair, and 1 poor. The excellent and good rate was 88.9%. CONCLUSIONS: With its design features, PSKA can effectively improve the range of motion and maximum flexion angle without compromising posterior stability. PSKA is suitable for both primary and revision total knee arthroplasty but caution should be taken for patellar complications.

Adult↗
PubMed2000

DAX-1 functions as an LXXLL-containing corepressor for activated estrogen receptors.

We have discovered that the orphan receptor DAX-1 (NROB1) interacts with the estrogen receptors ERalpha and ERbeta. Interaction occurs with ligand-activated ERs in solution and on DNA and is mediated by the unique DAX-1 N-terminal repeat domain. Each of the three repeats contains a leucine-rich receptor-binding motif, known as the LXXLL motif, which is usually found in nuclear receptor coactivators. We have demonstrated that DAX-1 functions as an inhibitor of ER activation in mammalian cells and suggest a mechanism involving two sequential events, occupation of the ligand-induced coactivator-binding surface and subsequent recruitment of corepressors. Accordingly, we propose that DAX-1 itself acts as a corepressor for ERs. Because DAX-1 is coexpressed with ERs in reproductive tissues, these interactions could play significant roles by influencing estrogen signaling pathways. Our results point at functional similarities between DAX-1 and the orphan receptor SHP (NROB2) in that they have acquired features of transcriptional coregulators that are unique for members of the nuclear receptor family.

DAX-1 Orphan Nuclear Receptor↗
PubMed2000

Induction paclitaxel in previously untreated, resectable, advanced squamous cell carcinomas of head and neck.

BACKGROUND: Previous Phase II trials evaluating paclitaxel as a single agent have produced objective response rates of 38-40%. However, in these studies patients had recurrent disease and had received previous treatment with chemotherapy, radiation, surgery, or some combination of the same. To the authors' knowledge, the study reported here is the first to examine the role of paclitaxel in affecting objective antitumor response, as a single agent, in a previously untreated patient population. METHODS: Patients with untreated, resectable, advanced squamous cell carcinoma of the head and neck were eligible for this Phase II trial. The treatment plan included paclitaxel 250 mg/m(2) administered by 24-hour intravenous infusion every 21 days for a total of 3 courses and primary prophylaxis with colony stimulating factor during each course of chemotherapy. Surgical resection was performed after recovery from the final course of chemotherapy. After adequate wound healing, patients received external beam radiotherapy (median dose to primary site, 55.8 Gray [Gy]; median dose to neck sites, 50.4 Gy). RESULTS: Forty-five patients were registered. Thirty-eight patients completed the planned chemotherapy, 41 patients underwent surgical resection, and 37 patients completed the intended radiotherapy. The objective response rate was 50% (10% complete response; 40% partial response). Severe or life-threatening (Grade 3 or higher) granulocytopenia or thrombocytopenia occurred in 78% and 27% of patients, respectively. Two patients died of sepsis. Seventy-one percent, 67%, and 91% of patients were free of local, lymph node, and distant recurrence, respectively, with a median follow-up of 37 months. The 4-year overall survival and disease-related survival rates were 44.4% and 52.9%, respectively. CONCLUSION: The authors conclude that paclitaxel is an active agent in patients with advanced head and neck carcinoma. However, the overall disease control, achieved by using paclitaxel as induction therapy, did not appear to be better than that achieved with standard treatment methods. Combined modality regimens with concurrent chemotherapy and radiotherapy have demonstrated more promise.

Adult↗
PubMed2000

Effect of CO(2) and CHF(3) on the Solubilization of Protein in Reverse Micelles.

The effect of dissolved CO(2) and CHF(3) on the precipitation of bovine serum albumin (BSA) from reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in 2,2,4-trimethylpentane (iso-octane) has been studied at 308.15 K. It was found that BSA can be precipitated completely by CO(2) while the AOT and water remain in the iso-octane continuous phase. This opens up a possibility for recovery of protein solids directly from reverse micellar solutions. CHF(3) is also an effective agent for precipitation of BSA in the reverse micelles when the expansion coefficient of CHF(3) exceeds 0.4. However, the condition required for complete removal of the BSA using CHF(3) results in some precipitation of AOT and water from the solution. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Structure and mechanism of homoserine kinase: prototype for the GHMP kinase superfamily.

BACKGROUND: Homoserine kinase (HSK) catalyzes an important step in the threonine biosynthesis pathway. It belongs to a large yet unique class of small metabolite kinases, the GHMP kinase superfamily. Members in the GHMP superfamily participate in several essential metabolic pathways, such as amino acid biosynthesis, galactose metabolism, and the mevalonate pathway. RESULTS: The crystal structure of HSK and its complex with ADP reveal a novel nucleotide binding fold. The N-terminal domain contains an unusual left-handed betaalphabeta unit, while the C-terminal domain has a central alpha-beta plait fold with an insertion of four helices. The phosphate binding loop in HSK is distinct from the classical P loops found in many ATP/GTP binding proteins. The bound ADP molecule adopts a rare syn conformation and is in the opposite orientation from those bound to the P loop-containing proteins. Inspection of the substrate binding cavity indicates several amino acid residues that are likely to be involved in substrate binding and catalysis. CONCLUSIONS: The crystal structure of HSK is the first representative in the GHMP superfamily to have determined structure. It provides insight into the structure and nucleotide binding mechanism of not only the HSK family but also a variety of enzymes in the GHMP superfamily. Such enzymes include galactokinases, mevalonate kinases, phosphomevalonate kinases, mevalonate pyrophosphate decarboxylases, and several proteins of yet unknown functions.

Adenosine Diphosphate↗
PubMed2000

Applications of the sulfinimine-mediated asymmetric strecker synthesis to the synthesis of alpha-alkyl alpha-amino acids.

Addition of Et(2)AlCN and i-PrOH to ketosulfinimines (N-sulfinyl imines) affords corresponding alpha-alkyl alpha-amino nitriles in moderate to good yields. The diastereoselectivity is largely dependent on the E/Z isomer ratio of the ketosulfinimine. Hydrolysis of the diastereomerically pure amino nitriles affords enantiopure alpha-alkyl alpha-amino acids in moderate to good yields.

Amino Acids↗
PubMed2000

BRCA1 and cell signaling.

The breast cancer and ovarian cancer susceptibility gene BRCA1 encodes a nucleoprotein whose mutations or aberrant expression is associated with both inherited and sporadic cancers. Studies over the last 6 years have suggested that BRCA1 may function as a scaffold in the assembly of a multi-protein complex, which plays a role in gene transcription, DNA damage repair, and transcription-coupled DNA damage repair. In this review, we discuss the implications drawn from the studies of BRCA1-interacting proteins and the cellular signaling pathways that may be involved in controlling the functions of BRCA1.

Animals↗
PubMed2000

Vertigo in MS: utility of positional and particle repositioning maneuvers.

A 4-year experience with new-onset vertigo in a university-based MS population was retrospectively reviewed. Of 1,153 patients with MS, 25 could be clinically evaluated during the vertiginous episode. Of these, 13 (52%) were diagnosed with benign paroxysmal positioning vertigo and eight (32%) had acute MS exacerbations with corresponding lesions within the brainstem. All patients diagnosed with benign paroxysmal positioning vertigo were treated successfully with particle repositioning maneuvers.

Adult↗
PubMed2000

NMR studies of the association of cytochrome b5 with cytochrome c.

In an effort to gain greater insight into the molecular mechanism of the electron-transfer reactions of cytochrome b(5), the bovine cytochrome b(5)-horse cytochrome c complex has been investigated by high-resolution multidimensional NMR spectroscopy using (13)C, (15)N-labeled cytochrome b(5) expressed from a synthetic gene. Chemical shifts of the backbone (15)N, (1)H, and (13)C resonances for 81 of the 82 residues of [U-90% (13)C,U-90% (15)N]-ferrous cytochrome b(5) in a 1:1 complex with ferrous cytochrome c were compared with those of ferrous cytochrome b(5) in the absence of cytochrome c. A total of 51% of these residues showed small, but significant, changes in chemical shifts (the largest shifts were 0.1 ppm for the amide (1)H, 1.15 for (13)C(alpha), 1.03 ppm for the amide (15)N, and 0.15 ppm for the (1)H(alpha) resonances). Some of the residues exhibiting chemical shift changes are located in a region that has been implicated as the binding surface to cyt c [Salemme, F. R. (1976) J. Mol. Biol. 10, 563-568]. Surprisingly, many of the residues with changes are not located on this surface. Instead, they are located within and around a cleft observed to form in a molecular dynamics study of cytochrome b(5) [Storch, E. M., and Daggett, V. (1995) Biochemistry 34, 9682-9693](.) The rim of this cleft can readily accommodate cytochrome c. Molecular dynamics simulations of the Salemme and cleft complexes were performed for 2 ns and both complexes were stable.

Amino Acid Sequence↗
PubMed2000

Regulation of apoptosis at cell division by p34cdc2 phosphorylation of survivin.

The interface between apoptosis (programmed cell death) and the cell cycle is essential to preserve homeostasis and genomic integrity. Here, we show that survivin, an inhibitor of apoptosis over-expressed in cancer, physically associates with the cyclin-dependent kinase p34(cdc2) on the mitotic apparatus, and is phosphorylated on Thr(34) by p34(cdc2)-cyclin B1, in vitro and in vivo. Loss of phosphorylation on Thr(34) resulted in dissociation of a survivin-caspase-9 complex on the mitotic apparatus, and caspase-9-dependent apoptosis of cells traversing mitosis. These data identify survivin as a mitotic substrate of p34(cdc2)-cyclin B1 and suggest that survivin phosphorylation on Thr(34) may be required to preserve cell viability at cell division. Manipulation of this pathway may facilitate the elimination of cancer cells at mitosis.

Amino Acid Sequence↗
PubMed2000

BRCA1 physically and functionally interacts with ATF1.

BRCA1, a breast and ovarian cancer susceptibility gene, encodes a 220-kDa protein whose precise biochemical function remains unclear. BRCA1 contains an N-terminal RING finger that mediates protein-protein interaction. The C-terminal domain of BRCA1 (BRCT) can activate transcription and interacts with RNA polymerase holoenzyme. Using the yeast two-hybrid system, we identified an interaction between the BRCA1 RING finger and ATF1, a member of the cAMP response element-binding protein/activating transcription factor (CREB/ATF) family. We demonstrate that BRCA1 and ATF1 can physically associate in vitro, in yeast, and in human cells. BRCA1 stimulated transcription from a cAMP response element reporter gene in transient transfections. BRCA1 also stimulated transcription from a natural promoter, that of tumor necrosis factor-alpha, in a manner dependent on the integrity of the cAMP response element. These results implicate BRCA1 in transcriptional activation of ATF1 target genes, some of which are involved in the transcriptional response to DNA damage.

Activating Transcription Factor 1↗
PubMed2000

Cloning, mapping and genomic organization of a fish C-type lectin gene from homozygous clones of rainbow trout (Oncorhynchus mykiss).

Utilizing a splenic cDNA library and rapid amplification of cDNA 5' ends (5'-RACE), a C-type lectin gene was cloned from a homozygous cloned rainbow trout. The 1176 bp cDNA contains a 714 bp open reading frame from which a 238-amino-acid (aa) (27 kDa) protein was deduced. It was confirmed that this protein belongs to the C-type animal lectins, and is a type II membrane receptor. The predicted protein from this sequence contains a 48 aa cytoplasmic domain, a 20 aa transmembrane domain (TM), a 46 aa stalk region and a 124 aa carbohydrate-recognition domain (CRD). The stalk region contains a leucine-zipper, and an N-glycosylation site was also found in the CRD. Sequence alignment and phylogenetic analysis of the CRD indicate that the protein has similarity with human dendritic cell immunoreceptor (DCIR), gp120 binding C-type lectin (gp120BCL) and mammalian hepatic lectins. The N-terminus (aa 4-183) has similarity with NKG2, a group of C-type lectin receptors important in human natural killer cell function. The genomic DNA (gDNA) containing this gene was amplified and sequenced. The 4569 bp gDNA contains five exons and four introns. The first three exons encode the cytoplasmic domain, the TM and stalk region, respectively. Unlike the other type II C-type lectin receptors in which the CRD was encoded by three exons, the CRD of this lectin was encoded by two exons. A transposon Tc1-like fragment was found in intron III. Intron IV is composed of a simple repeat. Tissue-specific expression of the gene was studied by RT-PCR, and it was mainly expressed in spleen and peripheral blood leukocyte (PBL). Using AluI to digest the fragment containing exon I, intron I and exon II, an RFLP was produced between the sequences of this gene in two cloned fish, OSU 142 and Arlee (AR). Seventy-one doubled haploids (DH) of OSU X AR were screened, and the gene was mapped to linkage group XIV on the published map (Young et al., Genetics 148 (1998) 839).

Amino Acid Sequence↗
PubMed2000

Differential alterations in antioxidant capacity in cells from Alzheimer patients.

Oxidative stress occurs in brains of Alzheimer's disease (AD) patients. A major question in AD research is whether the oxidative stress is just secondary to neurodegeneration. To test whether oxidative stress is an inherent property of AD tissues, the ability of cultured fibroblasts bearing the AD Presenilin-1 246 Ala-->Glu mutation to handle reactive oxygen species (ROS) was compared to controls. Although ROS in cells from AD subjects were only slightly less than cells from controls under basal conditions (-10%) or after exposure to H(2)O(2) (-16%), treatment with antioxidants revealed clear differences. Pretreatment with DMSO, a hydroxyl radical scavenger, reduced basal and H(2)O(2)-induced ROS levels significantly more in cells from controls (-22%, -22%) than in those from AD subjects (-4%, +14%). On the other hand, pretreatment with Trolox diminished H(2)O(2)-induced ROS significantly more in cells from AD (-60%) than control subjects (-39%). In summary, cells from AD patients have greater Trolox sensitive ROS and less DMSO sensitive ROS than controls. The results demonstrate that fibroblasts bearing this PS-1 mutation have altered means of handling oxidative stress and appear useful for determining the mechanism underlying the altered redox metabolism.

Adult↗
PubMed2000

Visualization of a functional Galpha q-green fluorescent protein fusion in living cells. Association with the plasma membrane is disrupted by mutational activation and by elimination of palmitoylation sites, but not be activation mediated by receptors or AlF4-.

To investigate how G protein alpha subunit localization is regulated under basal and activated conditions, we inserted green fluorescent protein (GFP) into an internal loop of Galpha(q). alpha(q)-GFP stimulates phospholipase C in response to activated receptors and inhibits betagamma-dependent activation of basal G protein-gated inwardly rectifying K(+) currents as effectively as alpha(q) does. Association of alpha(q)-GFP with the plasma membrane is reduced by mutational activation and eliminated by mutation of the alpha(q) palmitoylation sites, suggesting that alpha(q) must be in the inactive, palmitoylated state to be targeted to this location. We tested the effects of activation by receptors and by AlF(4)(-) on the localization of alpha(q)-GFP in cells expressing both alpha(q)-GFP and a protein kinase Cgamma-red fluorescent protein fusion that translocates to the plasma membrane in response to activation of G(q). In cells that clearly exhibit protein kinase Cgamma-red fluorescent protein translocation responses, relocalization of alpha(q)-GFP is not observed. Thus, under conditions associated with palmitate turnover and betagamma dissociation, alpha(q)-GFP remains associated with the plasma membrane. These results suggest that upon reaching the plasma membrane alpha(q) receives an anchoring signal in addition to palmitoylation and association with betagamma, or that during activation, one or both of these factors continues to retain alpha(q) in this location.

Aluminum Compounds↗
PubMed2000

The multimerization of human immunodeficiency virus type I Vif protein: a requirement for Vif function in the viral life cycle.

The Vif (virion infectivity factor protein of human immunodeficiency virus type I (HIV-1) is essential for viral replication in vivo and productive infection of peripheral blood mononuclear cells, macrophages, and H9 T-cells. However, the molecular mechanism(s) of Vif remains unknown and needs to be further determined. In this report, we show that, like many other proteins encoded by HIV-1, Vif proteins possess a strong tendency toward self-association. In relatively native conditions, Vif proteins formed multimers in vitro, including dimers, trimers, or tetramers. Through in vivo binding assays such as coimmunoprecipitation and the mammalian two-hybrid system, we also demonstrated that Vif proteins could interact with each other within a cell, indicating that the multimerization of Vif proteins is not simply due to fortuitous aggregation. Further studies indicated that the domain affecting Vif self-association is located at the C terminus of this protein, especially the proline-enriched 151-164 region. Moreover, we found that a Vif mutant with deletion at amino acid 151-164 was unable to rescue the infectivity of vif-defective viruses generated from H9 T-cells, suggesting that the multimerization of Vif proteins could be important for Vif function in the viral life cycle. Our studies identified a new feature of Vif and should accelerate our understanding of its role in HIV-1 pathogenesis.

Animals↗